Process of producing aluminum fluoride



Patented Oct. 7, 1941 PATENT OFFICE PROCESS OF PRODUCING ALUMINUM FLUORIDE Leopold Kalil, Berlin, Germany, assignor to the firm Ruetgers'werke-Aktiengesellschaft, Berlin,

Germany 6 Claims.

This invention relates to a process for the preparation of aluminum fluoride. It is known that aluminium sulphate reacts with fluor spar according to the following equationz o o 1 mason+2oarteAnmso4+2casor for example; finely pulverized fluor spar is treated; with a saturated aqueous solution of aluminium sulphate, thefluor spar is converted into calciuin sulphate, and at the same time a solution of the. double salt A12F4SO4 is. obtained. The reaction can be facilitated by heating. After the reaction has been finished, the solution of said double salt can be separated from 3Ai2i'isori4Alie+Ah(so-m. fi hejsolid double salt as well as' its aqueous solution can be subjected to such decomposition by heating. w If the solid double salt has been decomposed by heating, a mixture pi aluminium salts is obtained; the separation of this mixture into its components may be performed by treatingthe mixture with water, whereby the aluminium sulphate is dissolved and as an undi'ssolved residue aluminium fluoride is obtained.

decomposition of an aqueous solution of the fluor-aluminmmsulphate double salt according to the above equation, is carried out by heating the solution preferably under pressure n an autoclave to about 200-300 0. The decomposition and theseparation of aluminium fluoride irom the solution start for instance at about igiOF Qjand theseparation is completed at about 2009300 C.

Thus, the; treatment of the aqueous solution in an autoclave yields a mixture of solid aluifiuoride and a. solution of aluminium sulphate'. solution can be used again for the cenyersicn of fluor fipar. A H

The process according to my present invention No Drawing. Application February 4, 1939, Serial No. 254,601. In GermanyMarch 9,1938

can be used for the treatment of fluor spar which contains higher amounts of silicic acid, without the danger of contaminating the aluminium fluoride with silicic acid.

Example 1.-100 kilograms of finely pulverized fluor spa-r are boiled under vigorous stirring with a-solution of 2'70 kilograms of A12(SO4) 3.18 320 in 1000 kilograms of water for 3 hours. The solution of A12F4SO 4 thus obtained is separated from the precipitate, by filtration, and is heated in an autoclave to about 200 C. for 3 hours. The mixture obtainedis subjected to filtration whereby solid aluminium fluoride and a solution of aluminium sulphate are obtained. The aluminium fluoride is dried, and the solution is used for further treatment of fluor spar. Before such treatment a further amount of aluminium sulphate may be added to the solution.

In carrying out my present invention the proportion between fluor spar and aluminium sulphate, and the concentration of the aluminium sulphate solution, as well as the concentration of the solution of A12F4SO4, which is subjected to heating under pressure, may be varied within be carried out as a discontinuous treatment or as a continuous process. In the continuous process a solution of A12F4SO4 is continuously introduced into, and the decomposed solution is continuously removed from the autoclave.

Example 2.-100 kilograms of finely pulverized fluor spar are boiled under vigorous stirring with a solution of 270 kilograms of A12(SO4)3.18H2O a in 1000 kilograms of water for 3 hours. The solution of AlzF-(SO; thus obtained is separated from the calcium sulphate by filtration, and is then evaporated. The evaporation may be carried out at ordinary atmospheric or at reduced pressure. The solid mass thus obtained is heated gradually to about 250 C., and kept for 3-4 hours at this temperature. The heating may be effected in a container, the walls of which are heated to the necessary temperature or, for instance, by hot gases which come into contact with the mass to be heated, and do not affect the duality of the compounds to be obtained. After cooling the mass is comminuted, and treated with hot water until the aluminium sulphate is a "completely dissolved. The insoluble residue consists of aluminium fluoride which is obtained with a yield closely "approaching the theoretical value.

I have further found that other salts of aluminium may be used instead of aluminium sulphate for carrying out the present process.

i' t By treating fluor spar, for instance, with a sowide limits. Such heating under pressure may lution of A1013, .AlBI'3 or A113, solutions of fluorcontaining double salts of the formula AlF3.A1C13,

AlF3.A1BI3 and AlF3.A1I3 are formed according to the following equations:

If the solutions, which are obtained from fluor spar according to the above equations, and, which also contain CaClz, CaBrz, CaIz or Ca(NOs)2 in addition to the fluor-containing double salts, are heated under pressure in closed containers to temperatures over 100 C., preferably to 200-300 0., the double salts contained in the solutions are decomposed and .AlFs is precipitated. The precipitation starts at about 140 C. and is completed at 200-300 C. A mixture of insoluble aluminium fluoride and two dissolved salts, for instance AlCl3+CaCl2, AlBr3+CaClz, AlIs-l-CaIz, (Al(NO3)3+Ca(NO3)2, is thus obtained.

According to a modification of my process the solutions obtained from fluor spar'in the above described manner, may be evaporated and the mass obtained as a residue may be decomposed by heating it to about ZOO-300 C. The residue is extracted with water whereby the soluble salts are dissolved, and aluminium fluoride'is obtained as insoluble remainder. The solutions thus obtained are freed from the calcium salts by precipitation and may then be used for the further treatment of fluor spar. The precipitation of the calcium salts may, for instance, be efiected by means of aluminium sulphate, according to the following equation, whereby the original composition of the solution is restored:

'C. The mixturecontaining precipitated AlFs and a'solution of Al'(NOs)3and Ca(NOs)z is filtered, the aluminium fluoride is dried, and the solutionof A1(NO3)3 and Ca(NOa)2 can be used again for the treatment of fluor spar, preferably after adding afurther amount of Al(NO3)3 and removing the. calcium salt from the solution by precipitation. r

7 Example 4,-100 kilograms-of fluor spar are boiled for 3 hours with a solution of 640 kilograms of Al(NO3 )3.9I-I O in 1500 liters of water,

and the solution obtained is separated from the undissolved impurities by filtration.

. Thewater is then driven out from the solution shown by the folof A1F3.A1(NO3)3 and Ca(NO3)2 by evaporation, and the residue is heated gradually to about 250 C. The mass is kept at this temperature for about 3-4 hours. After cooling, the mass is comminuted and treated with water until practically all of the A1(NO3)3 and Ca(NO3)z are dissolved. The residue consists of aluminium fluoride which is obtained with a yield of almost Example 5.l00 kilograms of finely pulverized fluor spar are boiled for about 3 hours with a solution of kilograms of A1C13 in 1300 liters of water. The solution obtained is separated from the undissolved impurities by filtration, and is further worked up as described in Example '3.

- Example 6.--l00 kilograms of fluor spar are boiled for about 3 hours with a solution of 230 kilogramsof AlBra in 1400 kilograms of water, and the solution obtained is separated from the undissolved impurities by filtration. The solution is then further worked up as described in Example 4.

By decomposition temperature in my present specification and claims it is to be understood temperatures are those at which the decomposition of the solid double salt A12F4SO4 and similar double salts, which contain aluminium fluoride and another salt of aluminium, or the decomposition of an aqueous solution ofsaid salts, takes place. Such decomposition starts-at temperatures over 100 C., for instance atl40 0., and can be completed preferably at temperatures of about 2'00-300 0.. Higher temperatures, which do not cause decomposition of the individual com: ponents of ,saiddouble salts, may also be used.

I claim;

l. A process for obtaining aluminum fluoride from a water soluble double salt consisting: of aluminum fluoride and another salt of aluminum, said process consisting of decomposing said water soluble double salt into aluminum fluoride and said other salt of aluminum by heating at the decomposition temperature, above 100 (2., or said double salt, and separating aluminum fluoride from the other aluminum salt.

2. A process for obtaining aluminum fluoride from a water soluble double salt consisting of aluminum fluoride and another sal-tof aluminum, said process consisting of decomposing said water soluble doublesalt into aluminum fluoride and said other salt of aluminum by heating at the decomposition temperature, above 100 C., oi said double salt, and separating aluminum fluoride fromthe other aluminum sale by dissolving said other aluminum salt in water. V Y

3. A process for obtaining aluminum fluoride fromthe water soluble double salt Al2F-1SQ4, said process consisting of decomposing said double salt into aluminum fluoride and aluminum sulfate by heating at the decomposition temperature, above 100 0., of said double salt, andseparating aluminum fluoride from aluminum sulsaid process'consisting of decomposing said water soluble double saltinto aluminum fluoride and said other salt of aluminum by' heating at the decomposition temperature, above 100? C., oian aqueous solution of said double salt, andsepae rating aluminum fluoride from the solution of the other aluminum salt.

5. A process for'obtaining aluminum fluoride from a water soluble double salt-consisting of a m fluoride and her San of aluminum;

said process consisting of decomposing said water soluble double salt into aluminum fluoride and said other salt of aluminum by heating under pressure at the decomposition temperature, above 100 C., of an aqueous solution of said double salt, and separating aluminum fluoride from the solution of the other aluminum salt by filtration.

6. A process for obtaining aluminum fluoride from the water soluble double salt A12F4SO4, said process consisting of decomposing said double salt into aluminum fluoride and aluminum sulfate by heating an aqueous solution of said double salt to about 200-300 C. in an autoclave, and separating aluminum fluoride from the aluminum sulfate solution by filtration.

LEOPOLD KAI-IL. 

